The Heart of the Navy’s Next Destroyer

When the first new Flight III Arleigh Burke-class destroyer enters service with the U.S. Navy in 2019, it will be equipped with a new radar roughly 30 times more powerful than the long-serving Lockheed Martin SPY-1 system found on current Aegis warships. Called the air and missile defense radar (AMDR), the new sensor is expected to exponentially increase the ship’s performance in simultaneously defending the Fleet against both air-breathing and ballistic-missile threats. The key technology that enables such high performance is a semiconductor called gallium nitride (GaN).

“It is definitely one of the key enabling technologies,” said Captain Douglas Small, Naval Sea Systems Command’s AMDR program manager, during an interview with USNI News. “We’re basically in the Flight III going to deliver over 30 times the radar capability for about twice the input power.”

In addition to having 30 times the sensitivity of the current SPY-1 radar, the AMDR’s dynamic range will be greatly improved, particularly in areas with lots of interference from other emitters, jammers, and clutter. Another key attribute will be the AMDR’s digital beam-forming capability, which enables rapid horizon-to-horizon surveillance of air targets while simultaneously devoting much more energy toward ballistic missile defense. Small credits the unique properties of GaN for a large part of the large increase in performance. “It is a tremendous improvement enabled by the gallium nitride to be able to do that,” he said.

Another aspect of the AMDR’s performance will be the result of the radar’s active electronically scanned array (AESA) antennas. Unlike the SPY-1, which is a passive phased-array radar with one large transmit/receive (T/R) element, the AMDR will use many thousands of small T/R modules to form its antenna. About a thousand or so T/R modules will be grouped together to form a sub-array. Several sub-arrays will then make up the radar.

The benefit of such a configuration is that it allows for scalability. But it also affords much more precise control of the radar beam—enabling such capabilities as digital beam-forming. It also eases maintenance since the loss of a few modules has a negligible impact on the overall performance of the system.

Gallium nitride offers huge improvements in performance over gallium arsenide (GaAs)–based systems, which were developed for previous generations of AESA radars that are usually found on fighter aircraft. GaN-based T/R modules have the potential to provide better than five times the power per element of GaAs-based T/R modules in the same amount of space. Effectively that means that fewer high-powered GaN T/R modules are needed to match a larger number of low-power GaAs-based chips. GaN is also much more efficient in converting electrical power into radio waves.

It is because of GaN’s power density that the Navy is able to get the same required performance out of the current 14-foot AMDR antenna. It had originally intended to use a much larger version, envisioned for the now-defunct CG(X) guided missile cruiser project. “The concept for the CG(X) was to carry a much larger radar specifically because of some of the assumptions that were made about where the ship would have to operate and those sorts of things,” Small said. “The radar that we are going to deliver to the Flight III has essentially the same capability as the one that would have been on the CG(X).” It will be smaller, but the requirements are “vastly similar.”

But there have been concerns about the readiness of GaN for a production program. During the early years of development of the GaN material, production yields for the semiconductor were low and rejection rates were high. Moreover, many devices that used the technology suffered from poor reliability due to the extreme electrical currents running through such a small space.

But those issues have been resolved, said Carl Herbermann, Northrop Grumman’s AMDR director, whose team is competing for the AMDR radar’s engineering and manufacturing development phase along with Lockheed and Raytheon. “Everything we’ve gotten to date indicates to us that the technology is ready for prime time,” he said. “The yields, and the improvement in those yields, both of which are happening at a faster rate than we would have anticipated.” The yields are already good enough for producing the AMDR, he said.

Northrop also has built numerous prototypes and conducted long-term tests on GaN-based radars—some of which lasted for more than 5,000 hours. Northrop is continuing accelerated life-cycle tests on the technology even now, and the results look very promising, Herbermann said. “That operational life wants to be in excess of a million hours and we see no issue with meeting that requirement,” he said.

As far as the Navy is concerned the GaN technology has proven itself. “For this application, we have proved it out and then some,” Small said. “Proved it out under really tough conditions for the radar and for a long, long time.” The AMDR technology development (TD) phase, which came to a close a few months ago, was designed to not only test the capability of the new radar but also its reliability under operationally representative conditions, he said. “All of the technology including the gallium nitride has been proven,” Small said. “Proven well and early in the TD phase.”

There have also been concerns among many critics that the Burke-class hull would not be able to handle the size, weight and cooling requirements of the AMDR, but Small said that should not be a problem. He said that while the new radar will be larger than the existing SPY-1 antennas, it would not “radically” change the superstructure of the warship. “It is slightly bigger than the current aperture,” Small said. “It’s nominally a 14-foot aperture for AMDR, the S-band array, whereas today it’s nominally a 12-foot aperture, so an extra foot on each side.”

Small is not the program manager for the Flight III Burke itself, but he said he is confident that the ship will have both the electrical power and the cooling necessary to mount the AMDR. “Absolutely, the ship can not only handle this radar, it’s going to be able to handle this radar and have sufficient margin to have the growth capacity that the Navy needs,” Small said.

Further, he noted that the AMDR was designed to be scalable right from the outset. That means it can very easily be adapted to fit a larger vessel with more power available. Or it could be scaled down to fit a smaller ship. “It certainly could be backfit [to older Aegis ships],” Small said. “But we have not looked in any great detail at what that would take. . . . It is not part of our program of record.”

Right now the program is set to go into source selection for the AMDR’s engineering and manufacturing development phase, Small said. He said he cannot talk about the details, but whatever radar is selected will have further software and hardware development ahead. It will also have to be tested extensively before it enters production to be delivered to the ship in 2019.

Small said that the AMDR, even with its advanced capabilities is proving to cost less than originally expected. “Not only are we going to deliver over 30 times the radar capability in sensitivity, we’re doing it for a lot less money than we thought we could even three years ago,” he said.

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About Dave Majumdar

Dave Majumdar has been covering defense since 2004. He has written for Flight International, Defense News and C4ISR Journal. Majumdar studied Strategic Studies at the University of Calgary and is a student of naval history.

He’s leaving off that the Burke hull has no room for the massive cooling and power loads. He’s leaving off that because they’re using a Burke hull the first dozen AMDR ships won’t even have the full AMDR, they’ll have the same SPQ-9B mechanically-scanned radar dish of the current boats in place of the proper X-band array. And he’s leaving off that if by some miracle we CAN cram it all onto there, the hull will be so overloaded it won’t have a prayer of handling any future upgrades.